Modulating valve assembly for railroad car brake cylinders

ABSTRACT

A modulating valve for railroad car brake cylinders to adapt them for operation with composition brake shoes, in the form of an assembly comprising a bracket plate arranged for connection in the brake cylinder pipe, at a convenient location between the brake cylinder and the AB control valve, in place of a portion of the brake cylinder pipe removed for that purpose, and a modulating valve mounted on the bracket plate and in communication with the brake cylinder pipe and brake cylinder to limit the fluid pressures supplied to the brake cylinder so that composition brake shoes will deliver the proper brake applying force to the truck wheels without interferring with proper operation of existing brake control equipment.

This Application is a continuation-in-part of our Application Ser. No.813,005, filed July 5, 1977, now U.S. Pat. No. 4,093,315, granted June6, 1978, the entire disclosure of which is incorporated herein by thisreference.

This invention relates to a modulating valve assembly for use withrailroad car pneumatic brake equipment, and more particularly, to amodulating valve assembly for connection to the car brake cylinder toadapt the brake cylinder to deliver the amount of brake applying forceto the truck wheels that is proper for the modern composition brakeshoes.

The now familiar composition type brake shoe has a much highercoefficient of friction than the older type cast iron shoes, and whenapplied to the car truck wheels requires a significantly less shoeapplying pressure than required for cast iron shoes to effect the samedegree of braking on the car wheels. However, it is well known in therailroad field that merely reducing brake equipment actuating pressuresis no answer to successfully equipping with composition shoes a car withrigging designed for use with cast iron shoes. Furthermore, modificationor complete replacement of car rigging designed for use with cast ironshoes to conform to requirements where composition shoes are to be usedis too costly to be practical from the standpoint of updating most olderfreight cars.

A conventional approach to the problem is to convert existing brakecylinders designed for use with cast iron shoes into a smaller effectivesize. See, for instance, Salton U.S. Pat. No. 3,260,169.

The present invention is concerned with equipping existing brakecylinders of brake rigging designed for using cast iron shoes with amodulating valve that is arranged so that composition shoes if appliedto the car in question will act on the truck wheels with a brake forcethat is a predetermined percentage of the braking force required forcast iron shoes, without having to physically modify the brake cylinderas such.

A principal object of the invention is to provide a modulating valveassembly for connection to brake cylinders of rigging designed for usewith cast iron shoes, so that the brake cylinder itself need not bemodified, other than by application thereto of the valve assembly, todeliver the braking force appropriate when the car is equipped withcomposition shoes.

Another important object of the invention is to provide a modulatingvalve assembly adapted for connection to brake cylinders designed foruse with cast iron shoes for converting such cylinders to use withcomposition shoes, that may be applied as a unit to the brake cylinderpipe between the connection of the brake cylinder pipe to the brakecylinder head and the AB control valve without requiring structuralmodification of the cylinder or its operating parts, and where there isinsufficient room adjacent to the brake cylinder head for application ofthe bracket plate of our said Application.

Yet another important object of the invention is to provide a modulatingvalve arrangement for use with brake cylinders designed for use withcast iron shoes that is arranged for readily providing for any givenapplication, any desired ratio of composition shoe braking force to castiron shoe braking force that may be appropriate for the particular carinvolved.

Other objects of the invention are to provide a modulating valvearrangement that operates equally well under both low and full pressureconditions, that insures that the composition shoes will bear againstthe truck wheels with the force required by the AAR at 10 pounds brakefluid pressure, and that is economical of manufacture, easy to assembleand install, and long lived and reliable in operation.

In accordance with the invention, a modulating valve assembly isprovided comprising a bracket plate that is arranged to incorporate theassembly in the brake cylinder pipe between the brake cylinder end ofthe brake cylinder pipe and the AB control valve in situations wherethere is insufficient room at the head end of the brake cylinder forapplication thereto of the bracket plate of our said application.

The revised bracket plate mounts the modulating valve device that isformed, in accordance with said Application, to provide communicationbetween the upstream portion of the brake cylinder pipe and the valvedevice, and between the valve device and the downstream portion of thebrake pipe, and thence the brake cylinder, with the modulating valvedevice being arranged to supply to the brake cylinder the actuatingfluid under pressure that will cause the composition shoes to apply tothe truck wheels the braking force that is appropriate for compositionshoes, as compared to the older cast iron shoes.

The modulating valve device itself comprises a housing defining a cavityhaving a differential valve member mounted across the cavity to define afirst or fluid flow cut off chamber and a second or differential valveclosing chamber on either side of the valve member, and for flexingmovement axially of the valve member to seat against an annular valveseat positioned in the indicated first chamber of the valve device. Thevalve device first chamber is in open communication with the upstreamportion or segment of the brake cylinder pipe through a first passageformed in the bracket plate, and a second passage formed in the bracketplate communicates the valve device second chamber with the brakecylinder through said valve seat and the downstream segment of the brakecylinder pipe. The differential valve member is mounted to be flexed,under the action of differential pressures acting on same, against thevalve seat for sealing off communication of the indicated bracket platesecond passage to the indicated valve device first chamber, and againsta spring bias tending to hold the valve seat open. The valve devicesecond chamber is in free communication with the bracket plate secondpassage, and the valve member has exposed in the respective valvechambers on either side of the valve member working areas of which theworking area exposed to the valve member second chamber is greater thanthe working area of same that is exposed to the valve device firstchamber by a predetermined ration, whereby when the valve chambers aresubject to fluid pressure supplied through the upstream portion of thebrake cylinder pipe, the valve member will be, as the fluid pressuresbuild up, subject to a differential pressure force that will bias sametowards sealing relation with the valve seat.

The differential valve member itself comprises a pair of spaced apartdiaphragms spanning the valve housing cavity and having their endsmounted in sealed relation within the housing to dispose said diaphragmsto define the indicated valve member working areas, and a compositepiston interposed between the diaphragms that includes an inner partcentered with respect to and overlying the valve seat of the valvedevice first chamber, and an outer part in circumambient relation to thepiston inner part. The piston parts are in close fitting lost motionrelation, with the piston outer part defining a bore receiving thepiston inner part, and with the piston outer part bore being larger thanthe indicated valve seat. A compression spring encircles the valve seatto bias the valve member away from same and engages the diaphragm thatopposes the valve seat and that is adapted to engage the valve seat whenthe predetermined differential force acts to close the valve memberagainst the valve seat. The valve seat is operably associated with anadjacent check valve that opens when the brakes are released toaccommodate fluid pressure discharge from the brake cylinder and out thebrake cylinder pipe in the usual manner.

The modulating valve is arranged so that, for minimum serviceapplications, it remains fully open, and brake cylinder pressure is noteffected, so that static preloads in the rigging (due to brake beams,brake adjusters, and the like) will be overcome and brake shoe contactwith the wheels is effected with the force required by the AAR at tenpoiunds brake cylinder pipe pressure. For higher brake cylinder pipepressure service applications, the modulating valve through theoperation of the differential valve member as coordinated with thecompression spring associated with same acts to limit the air pressuresupplied to the brake cylinder to provide the desired ratio ofcomposition shoe braking force to cast iron shoe braking force.

The differential valve member is arranged to accommodate accuratedesigning into any particular model of same the point during the brakestroke at which air flow to the brake cylinder is to be stopped at thedesired predetermined brake force ratio, while yet insuring that thebrake cylinder acts under full brake cylinder pipe pressure for minimumservice application whereby the static preloads in the rigging will beovercome. Further, the arrangement is such that the operating stroke ofthe differential valve member need only be on the order of 0.050 inch,and that destructive crushing of the portion of the valve diaphragm thatengages the valve seat for closing off fluid pressure flow to the brakecylinder is avoided.

Other objects, uses, and advantages will be obvious or become apparentfrom a consideration of the following detailed description and theapplication drawings in which like reference numerals indicate likeparts throughout the several views.

In the drawings:

FIG. 1 is a diagrammatic view in largely block diagram form indicatingthe principal air operated and operating components of a typicalrailroad freight vehicle, including a showing of the brake cylinder andbrake cylinder pipe as equipped in accordance with the practice of thepresent invention;

FIG. 2 is an end elevational view of the modulating valve assembly ofthis invention, including the bracket plate and the modulating valvedevice and volume chamber secured thereto, but with the brake cylinderpipe omitted;

FIG. 3 is a side elevational view of the bracket plate of FIG. 2 asincorporated in the brake cylinder pipe, but with the modulating valvedevice itself omitted;

FIG. 4 is a diagrammatic sectional view of the assembly shown in FIGS. 2and 3, showing the relation between the brake cylinder pipe, the bracketplate, and the modulating valve device of the invention, with partsbeing partially broken away and the valve assembly volume reservoirlargely omitted; and

FIG. 5 is an enlarged sectional view better illustrating the check valveemployed in the modulating valve of this invention.

However, it is to be distinctly understood that the specific drawingillustrations provided are supplied primarily to comply with therequirements of the Patent Laws, and that the invention is susceptibleof other embodiments that will be obvious to those skilled in the art,and which are intended to be covered by the appended claims.

GENERAL DESCRIPTION

Reference numeral 10 of FIG. 1 generally indicates the principal airoperated and air operating components of a typical railroad freight carair operated brake apparatus including the usual AB control valve 12 towhich is connected the familiar brake pipe 14, the auxiliary reservoir16, the emergency reservoir 18, and the brake cylinder 20. As usual, thecontrol valve 12 includes service portion 22 adapted to operate both aservice and an emergency rate of reduction in pressure of the fluid inthe car brake pipe 14 for supplying fluid (air) under pressure from theauxiliary reservoir 16 to brake cylinder pipe 24.

Control valve 12 also includes emergency portion 26 adapted to operateonly upon an emergency rate of reduction of pressure of the air in thebrake pipe 14 for supplying air under pressure from emergency reservoir18 to the brake cylinder 20.

Upon recharging of the brake pipe 14 on release of the brakes, controlvalve 12 operates to open the brake cylinder to atmosphere through pipe28 and retaining valve device 30. At the same time the recharging of thebrake pipe 14 effects the charging of the reservoirs 16 and 18 in theusual and well known manner. The service and emergency portions 22 and26 of control valve 12 are mounted on the opposite faces of the pipebracket 32 to which all pipe connections to the brake control valve 12are made, as is conventional, and as indicated in the showing of FIG. 1.Of course, AB valve 12 may also take the form of the newer ABD valve, asis well known in this field.

As to the brake cylinder 20 itself, it conventionally comprises theusual cylinder head 40 that is flanged for bolted application to theconventional flange of the usual brake cylinder shell 46. The head 40 isshaped to define the usual projecting hub portion 48 defining thefamiliar brake cylinder inlet port planar land portion against which issecured the usual flange type fitting 54 that couples the brake cylinderpipe 24 to the head 40, which fitting 54 is conveniently secured inplace by employing a pair of bolts applied to a pair of bolt holesformed in head 40 for that purpose, all as disclosed in our saidApplication.

In accordance with the present invention, the brake apparatus 10 isadapted for use in connection with rigging equipped with compositionshoes, by applying to the brake cylinder pipe 24 the modulating valveassembly 61 at a convenient location in the brake cylinder pipe 24(assuming the rigging in question has been designed for use with castiron brake shoes), where there is insufficient room at the head end ofthe brake cylinder 20 to employ the bracket arrangement of our saidApplication.

As indicated in FIGS. 2-4, the assembly 61 comprises bracket plate 62having secured to same modulating valve device 64 (FIG. 4), and volumereservoir 66.

Bracket plate 62 is formed with a pair of bolt receiving openings 68(only one is illustrated in diagrammatic FIG. 4) which receive thethreaded shanks 70 of bolts 72 that in accordance with the invention areemployed to secure a pair of fitting plates 54 on either side of thebracket plate 62 that are of the same type of flange type fitting plate54 conventionally employed to couple the brake cylinder pipe 24 tocylinder head 40. The brake pipe 24 is suitably interrupted at aconvenient location between its connection to valve 12 and the brakecylinder 20, the fitting plates 54 of FIGS. 3 and 4 are applied to thethus formed end portions 24A and 24B of the brake cylinder pipe 24 (forcoupling such end portions 24A and 24B to the bracket plate 62), andthen the bracket plate 62 is disposed between such fitting plates 54 andthe bolts 72 and their cooperating nuts 73 applied thereto to clamp thefitting plates to either side of the bracket plate 62 to couple theindicated brake cylinder pipe ends thereto, for operation of assembly 61in the manner disclosed in said Application, and as describedhereinafter.

Further in accordance with the invention, the bracket plate 62 isequipped with a bracing foot in the form of flange 81 that receivessuitable bolts 83 to anchor bracket 62 to a convenient adjacent carstructure 85 (flange 81 is omitted from the showing of FIG. 4).

Further in accordance with the invention, the bracket plate 62 is formedto define passage 90 having a port 92 which communicates with the brakecylinder pipe end 24B and a port 94 which communicates with valve device64. Passage 90 also communicates with the volume reservoir 66 at port96.

Bracket plate 62 is further formed to define passage 98 thatcommunicates with the valve device 64 at port 100 and communicates withthe brake cylinder pipe end 24A at port 102.

The valve device 64 is that shown in FIG. 6 of said application, andcomprises a housing 110 formed to define cavity 112 across which ismounted differential valve member 114 that defines the cavity 112 intothe respective chambers 116 and 118. The valve member 114 cooperateswith an annular valve seat 120 formed on a tubular member 122 to formair flow shut-off valve 121. Member 122 has its bore 124 incommunication with passage 126 formed in housing 110 and aligned withthe bracket plate port 100. The housing 110 is formed also to definepassage 128 that communicates between the bracket plate port 94 andchamber 116. The housing 110 further defines passage 130 thatcommunicates between the chamber 118 and a lateral extension 132 of thepassage 98 which is formed in bracket plate 62.

The valve member 114 of valve device 64 is spring biased away from seat120 by suitable compression spring 136.

Housing 110 is suitably flanged as at 138 for application thereto ofsuitable bolts 140 for securing the device 64 to bracket plate 62.

Operably associated with the tubular member 122 of valve device 64 ischeck valve 142 that is operative to accommodate air flow from the brakecylinder through brake cylinder pipe 24 and thence to retainer 30 onrelease of the brakes, as will be hereinafter described in detail.

The assembly 61, in general terms, functions to make available to thebrake cylinder 20 for minimum service operations the brake cylinder pipepressure at 100 percent to insure that the rigging static preloads areovercome for such minimum service applications. For normal or fullservice applications, the assembly 61 also functions to limit the airpressure build up in the brake cylinder 20 to a predetermined percentageof that for which the brake cylinder 20 was designed for use inconnection with cast iron shoes (for instance a percentage in the rangeof 50-60 percent), by the differential nature of valve member 114 andits cooperating chambers 116 and 118, whereby the valve member 114 seatsagainst the valve seat 120 to close the normally open valve 121 of thedevice 64. On release of the brakes, check valve 142 opens to releasethe air in the brake cylinder 20 through brake cylinder pipe 24 forexhaust through control valve 12 and retainer valve 30.

The modulating valve device 64 involves a number of spacificimprovements that are described hereinafter.

SPECIFIC DESCRIPTION

In the showing of FIG. 4, the bracket plate 62, the modulating valve 64,and the volume reservoir 66 are illustrated in positioning and shapingsomewhat displaced from the positioning of FIGS. 2 and 3 to facilitateillustration and description.

The bracket plate 62 may be formed in any suitable manner to define thepassages and porting indicated. It is flanged as at 150 for applicationthereto of the volume reservoir 66, which may be of any suitable type ofchamber defining vessel for the storage of air received from the bracketplate passage 90 through port 96 and suitable porting (not shown) formedin chamber 66. Suitable bolts 152 may be employed to secure the volumechamber 66 to the bracket plate 62. Plate 62 may be suitably grooved at153 to receive the respective O-ring seals 155 that are disposed aboutthe respective ports 92 and 102, and may be suitable marked as indicatedat 157 to indicate to the installer the correct positioning of theassembly 61 with regard to brake service pressure fluid flow throughbrake cylinder pipe 24.

The bracket plate 62 is formed to define planar land or surface 160against which housing 110 seats for application thereto of the mountingbolts 140 to bracket plate holes 162 through the housing bolts holes164. Suitable O-ring seals 166, 168 and 169 are employed between thehousing 110 and bracket plate 62 where indicated in FIG. 4 for sealingpurposes at the juncture of the passages 126, 128 and 130 with thecorresponding ports of the bracket plate 62.

The valve member 114 of valve device 64 is of special significance andconstruction and comprises an inner diaphragm 170 and an outer diaphragm172 operably associated with and receiving therebetween the compositepiston 174 that structurally comprises an outer annular piston part 176that receives in a lost motion manner an inner piston part 178. Thepiston parts 176 and 178 are in substantial coplanar relation betweenthe diaphragms 170 and 172, and are proportioned laterally of the valvemember 114 so that they may be engaged by both the diaphragms 170 and172 when aligned for this (in the plane of member 114). The housing 110comprises a base or pedestal 190 that is formed with flange 191 definingoutwardly facing land 192 on which is seated annular diaphragm mountingmember 194 on top of which is applied the housing closure cap 196, theseparts being suitably held together, as by employing suitable bolts 198applied to housing 110.

The diaphragms 170 and 172, which are formed from a suitable elastomericmaterial such as polyurethane, are in disc form having their rims 200clamped in seal tight relation against mounting member 194 by the actionof bolts 198 fixing cap 196 and member 194 to housing 110.

As indicated in FIG. 4, the diaphragm mounting member or component 194is formed with a stepped diameter opening 204 defining a flange 206 anda counterbore 208, with the outer piston part 176 being of roundedannular configuration and defining an outwardly directed radial flange210 that cooperates with the flange 206, and an inwardly directed radialflange 212 that freely receives the inner piston part 174 in the bore213 and counterbore 215 defined by same. The inner piston part 178defines outwardly directed radial flange 214 which cooperates with theflange 212 of the outer piston part 176.

The piston parts 176 and 178 are proportioned radially thereof andtransversely of the respective valve members 174 so that the outerpiston part is freely received within the diaphragm mounting component194, and the inner piston part 178 is freely received within the outerpiston part 176, as indicated in FIG. 4. Further, the flanges 206 and210, and the flanges 212 and 214, of the diaphragm mounting component194 and the piston parts respectively, are proportioned transversely ofthe valve member 114 (that is, in its direction of movement relative toseat 120) so that the outer piston part 176 will have some lost motionmovement relative to the diaphragm mounting component 194 in thedirection of movement of valve member 114, while the inner pistoncomponent 178 will have some lost motion movement with respect to theouter piston component 176 in the same direction.

It will also be observed that the inner piston part 178 defines a studor hub portion 220 having a generally planar inwardly directed workingsurface 222 having a diameter that exceeds both that of seat 120 and thetubular element 122 in which it is formed, and an outer working surface223 having a diameter that exceeds that of surface 222 such that thearea of surface 223 will exceed that of surface 222 by a predeterminedamount. The outer piston part 176 defines an inwardly directed workingsurface 224 that is annular in configuration and has an inner diameterthat exceeds that of the working surface 222, and an outer diameter thatis less than the diameter of bore 204 of the diaphragm mountingcomponent 194. Piston part 176 also defines an outwardly directedannular working surface 225 having inner and outer diameters such thatthe area of surface 225 exceeds that of surface 224 by a predeterminedamount.

In the embodiment of FIG. 4, the spring 136 bears against the outerpiston part 176, the spring 136 seating against inner diaphragm 170.

The cavity 112 of housing 110 is formed by the recessing 230 of housingbase 190, the recessing 232 of the cap 196, and the bores andcounterbores 204 and 208 of the diaphragm mounting member 194.

The housing recessing 230 and 232 is formed so that the area of thediaphragm 172 that is exposed by chamber 118 (which is thus the workingarea of diaphragm 172) exceeds the corresponding working area of thediaphragm 170 that is exposed by chamber 116, by a predeterminedpercentage which determines the differential operating force of thevalve device 64 that will operate same to close the valve 121 and shutoff air entry into the brake cylinder 20, at the pressure within thebrake cylinder that will provide the desired percentage of compositionshoe braking force on the car trunk wheels, as compared to the neededcorresponding braking force for cast iron shoes. Of course, thispercentage may be of any desired ratio depending on the application andobjectives of the particular installation involved, although levels inthe range of from about 50 percent to about 60 percent are frequentlyused. In one commercial form of the invention the ratios of the exposedareas of the respective diaphragms to their respective chambers in thevalve device 64 are such that the valve 121 closes when the pressure inthe brake cylinder 20 is approximately 56 percent of the pressure in thebrake cylinder pipe 24.

In addition, and in accordance with the invention, the piston parts 176and 178 are arranged such that for minimum service applications, thevalve device 64 operates to insure that the air pressure supplied to thebrake cylinder is at one hundred percent of brake cylinder linepressure, up to approximately 12 psi, so as to insure the aforementionedneeded brake shoe contact with the car wheels (as per AAR standards) forfull service and emergency applications, the valve device, whileoperating at the one hundred percent level up to about 12 psi brakecylinder pipe pressure, reverts to the proportional pressurerelationship required for composition brake shoes. This is achieved by,in addition to providing for the diaphragm working surface ratiodescribed above, having the inner and outer working surface areas ofpiston part 178 (that is not engaged by spring 136) in the indicateddesired ratio (56 percent in the referred to example), and the inner andouter working surface areas of the piston part 176 (that is engaged byspring 136) in a different and less ratio, (for instance, 35 percent),that considered together and coordinated with the spring pressureprovided by the spring 136 will hold the piston part 176 against movingtoward valve closure position (of valve 121) through the zero toapproximately 12 psi brake cylinder pipe pressure range, but which,above the approximate 12 psi level, will move the indicated piston partto its closure position.

Thus, in the preferred embodiment of FIG. 4, the inner piston part 178has its surfaces 222 and 223 in the examplary 56 percent relation. Theouter piston part 176 has its working surfaces proportioned in theindicated 35 percent ration.

At the point in the operation of the brake braking stroke where valve121 is fully closed, valve member 114 and both its piston parts willhave deflected under the differential pressures acting on same to seatthe inner diaphragm 170 against the valve seat 120, the differentialpressures involved having, in addition to moving to its closed positionthe piston part 178, overcome the biasing action of spring 136 for fullclosure movement of the other piston part 176, whereby the pressureacting in brake cylinder 20 will be at the desired level needed forcomposition shoes for a particular input pressure above 12 psi.

As input pressures to the brake cylinder pipe are increased above thedesign closure pressure for valve 121, valve 121 opens and recloses toprovide the higher pressure output to the brake cylinder but in thedesign proportion. The tubular member 122 has its end portion 240 formedto define the valve seat 20 and has its other end portion 242 threadedfor application to the threaded bore 244 defined by the housing base190, into which opens the housing passage 126 that communicates with theport 100 of bracket plate 62.

The check valve 142 (see FIG. 5) comprises a plurality of lateralopenings or parts 246 formed in the tubular member 122 that openexteriorly of the tubular member 122 in circumferential groove 248 aboutand within which is seated O-ring seal 250. The groove 248 is ofinwardly converging shape, including side walls 247 and 249 (at leastone of which is frusto conical in shape), and seal 250 is proportionedto seat entirely against the walls 247 and 249 and be spaced from ports246 when in its closed position, to define an annular air flowdistributing chamber 251 underlying seal 250 into which all of the ports246 open. Thus, when the O-ring seal 250 is in its retracted or closedposition shown in FIGS. 4 and 5, the openings 246 are sealed check valvefashion, against air flow through the openings 246 in bypassing relationto the valve seat 120. However, when the air pressure within the tubularmember 122 (and thus that within the brake cylinder and the brakecylinder pipe portion ending at 24A) exceeds that within the chamber 116(and thus that within the brake cylinder pipe 24 portion ending at 24B)a sufficient amount, the O-ring seal 250 under the pressure uniformlybuilding up on same in the chamber 251, dialates outwardly radiallythereof to open the check valve 142 for fluid flow outwardly of thebrake cylinder 20 through valve device 64 (by passing valve 121) andinto the brake cylinder pipe 24 through passage 90.

As indicated in FIG. 4, the valve housing base 190, diaphragm mountingmember 194, and cap 196, are formed with connecting passages 260, 262,and 264 that form housing passage 130 communicating the valve deviceouter chamber 118 with the bracket plate passage 98 through itsextension 132.

The space within valve member 174 is vented to atmosphere throughpassage 275 formed in housing member 194 (see FIG. 4). Seals similar toseals 166 and 168 are preferably employed where indicated in device 64at 277.

OPERATION

The brake equipment 10 is charged in the usual manner, fluid (air) underpressure being supplied to the brake pipe 14 by the usual locomotivebrake valve to operate the control valve 12 in the usual manner toeffect charging of the reservoirs 16 and 18. As usual, when the brakesare in released relation, the brake cylinder pipe and the brake cylinderare closed off from the fluid pressure in brake pipe 14 by the operationof control valve 12.

When it is desired to effect a service brake application, the brakevalve in the train locomotive is actuated to reduce the fluid pressurein brake pipe 14 an amount corresponding to the degree of brakeapplication desired. This reduction of pressure in the brake pipe 14causes the service portion 22 of control valve 12 to connect theauxiliary reservoir 16 through pipe 17 and pipe 24 to valve assembly 61and thence to brake cylinder 20. The air flow from brake cylinder pipesection represented by end portion 24A is into assembly 60 through port92, passage 90, and port 94 into passage 128 of valve device 64 and itschamber 116 whereby the air pressure in the chamber 116 bears againstthe exposed area of the diaphragm 170.

As long as valve 121 remains open, the air continues to flow through thevalve seat 120, the tubular member 122, the housing passage 126, theport 100, passage 98, and port 102 into the brake cylinder pipe sectionrepresented by end portion 24A and thence into the brake cylinder 20.

Within the valve device 64, the chamber 118 receives air under pressurefrom the bracket plate passage 98, its extension 132, and housingpassage 130. As the braking stroke is initiated and proceeds to minimumservice level application, the air pressure in chamber 116 plus thebiasing action of spring 136 holds the valve 121 open for transmittal ofthe air pressure fluid through assembly 61 at the desired one hundredpercent ratio relative to the pressure in the cylinder brake pipe, sothat the braking force at this stage of the braking stroke is the sameas for cast iron shoes, thereby insuring the desired application of thebrake shoes to the car wheel (against the resistance of static preloadsin the rigging) as required by AAR regulations.

However, when the brake pressure fluid pressure in brake cylinder pipeupstream of assembly 61 reaches the desired predetermined level, such asthe indicated 12 psi level, the differential nature of the valve device64 becomes effective to move the valve member 174 to the left of FIG. 4,with the objective of bringing the braking force limiting action ofdevice 64 into full effect as soon as possible in the subsequent brakingstroke.

As indicated, the working area of the diaphragm 172 exposed to chamber118 exceeds the working area of the diaphragm 170 that is exposed to thechamber 116 by the indicated predetermined ratio, and as the airpressure builds up in brake cylinder 20 to the desired percentage of theair pressure in pipe 24 upstream of assembly 61 (this percentage willgive the composition brake shoes with which the apparatus 10 is equippedthe desired percentage of braking force that cast iron shoes wouldhave), the force acting on the diaphragm 172 overcomes the action of theopposing fluid pressure generated force acting on the diaphragm 170 aswell as that of spring 136 to seat the valve member 174 against the seat120, thus closing off further air flow to the brake cylinder 20.

Also involved is the particular relationships of the areas of theopposed working surfaces 222, 223 and 224, 225 of the valve member outerand inner piston parts 176 and 178. As indicated, the piston part 17(that is not opposed by the respective spring 136) has its inner andouter working surfaces in the same ratio or proportion that the workingareas of diaphragm have to each other, while the other piston part 176has its inner and outer working surfaces in a lesser proportion, whichin combination with the biasing action of the springs 136, is effectiveto provide one hundred percent braking force up to the desired pressurelevel above 10 psi, for instance, about 12 psi, in the brake cylinderpipe, after which (assuming the braking action continues for full normalor emergency service) the valve member 174 is moved under thedifferential forces acting on it to give the braking force the desiredlimitation. Once valve 121 has closed, further increases in brakinginput pressure to assembly 61 will open valve 121 and effect closing ofsame to keep the working pressures in the brake cylinder 20 in thedesired ratio.

During this operation of the valve device 64, the check valve 142remains closed as the pressure in chamber 116 exceeds that withintubular member 122.

On release of the brakes, normal operating pressure in the brake pipe 14is restored by operation of the usual brake valve in the locomotive, andthis causes control valve 12 to close off communication between thereservoir 16 and brake cylinder pipe 24, and open brake cylinder pipe 24to communication to exhaust through pipe 28 and retainer valve 30. Thepressure in brake cylinder pipe section represented by end portion 24Bthus drops, and when the pressure in chamber 116 becomes less than theair pressure within the closed off valve 121 (and thus the brakecylinder 20), the check valve 142 opens to discharge the air trappedwithin the brake cylinder, through its openings 246, into chamber 116,by the O-ring 250 dialating under the air pressure differentialinvolved. As the air pressure reduces in the bracket plate passage 98,it also reduces in the chamber 118 to the point where spring 136 returnsthe parts of the valve member 174 to the position of FIG. 4, toautomatically set valve 121 for the next application of the car brakes.

In this connection, the differential air pressures acting on O-ring seal250 are uniform thereabout as the brake cylinder pressure acts on seal250 three hundred sixty degrees about check valve annular chamber 251.

The modulating valve device 64 has a number of significant aspects.

For instance, the arrangement of the valve 64 is such that when aminimum service application is made, no brake cylinder pressurereduction is effected by the differential nature of the valve member174, whereby brake shoe contact with the wheels is effected with theforce required by the AAR at a minimum brake application (approximatelyten psi brake cylinder pressure).

This result is achieved both by the biasing action of the spring 136,and the special nature of the composite piston 174. In the device 64,the spring 136 opposes piston outer part 176, and thus in device 64 theworking surfaces 222 and 223 of the piston inner part have the sameratio as the ratio of the working areas of diaphragms 170 and 172, whilethe working surfaces 224 and 225 of outer piston part 176 have theindicated lower ratio (the higher area involved in the indicated ratiosis on the outer or right side of the respective device 64, as viewed inFIG. 4). While the specific ratios employed will depend on the specificsof each particular application, the special cooperation provided by thevalve member 114 and spring 136 is concerned with providing one hundredpercent braking force for minimum service pressure, with the valvedevice 64 being operative to shift over to its full braking forcelimiting characteristic as the fluid braking pressure in the brakecylinder pipe 24 moves to and beyond 18 psi for full service conditions.

Thus, for minimum service braking, valve device 64 ordinarily willfunction only at the one hundred percent braking force level, assumingthe brake cylinder pipe pressure does not exceed the indicatedapproximate 12 psi level, while for greater service and emergency brakeapplications valve device 64 will function at both the one hundredpercent and the desired ratio design levels, with the device 64 beingarranged to shift operation between such levels as the braking fluidpressure of pipe 24 moves through the 12 to 18 psi range. The device 64is preferred as in operation its transition from the one hundred percentoperating level to the design operating level will change in arelatively small range of input pressure increases over the indicated 12psi level.

Another important feature of the invention is that the valve 121 willnot fully close until both its piston parts have deflected under thedifferential forces acting on the member 114 to its full position to theleft of FIG. 4.

This is because when the piston outer part 176 moves to the full amountof its movement to the left of FIG. 4, its flange 210 seats on flange206 of the diaphragm mounting member 194. As the piston inner part 178has lost motion movement with respect to the piston outer part 176, andthe spring 136 in seating on the diaphragm 170 bears against one of thepiston parts, movement of the outer piston part 176 under thedifferential forces acting on it, to the left of FIG. 4 does notnecessarily involve the same amount of movement of the inner piston part178. The respective piston parts 176 and 178 have their own areas ofcontact with the diaphragm 172 that is to actuate same to move same tothe left of FIG. 4 under the differential forces developed on valvemember 114. The thickness proportioning of the outer piston part flange210 and the diaphragm mounting member flange 212 are such that whenflange 210 seats against flange 206, the biasing action of spring 136 issufficient to hold the diaphragm 170 and thus the inner piston part 178spaced from seat 120 until the desired pressure level within the brakecylinder has been achieved.

Similarly, the flange 212 of the piston outer part and the flange 214 ofthe piston inner part are proportioned such that under pressureconditions operating within the valve device 64, should the flange 214seat on the flange 212 prior to flange 210 seating on flange 206, theouter piston part 176 will tend to hold the inner piston part 178 fromclosing diaphragm 170 against seat 120.

However, when the flange 210 of the outer piston part 176 seats againstflange 206 of the diaphragm mounting member 194, and flange 214 of theinner piston part 178 seats against the flange 212 of the outer pistonpart 176, the diaphragm 170 will be seated on seat 120 to close valve121.

It is a feature of the invention that the output pressure from assembly61 will be determined by the operating characteristics of the pistonpart 176 or 178 that moves last to its valve closing position. As longas one of these piston parts has not moved toward its valve closingposition, assembly 61 will operate at the one hundred percent level andpressure input will be equal to pressure output.

It will be noted also that the diaphragms 170 and 172 are each singlepart or piece diaphragms of the nonrolling type. Since rolling diaphragmtype flexture is not involved in the valve device 64, reinforcing of thediaphragms is not required. The valve member 114 is designed for shortstroke operation, a closure stroke of about 0.050 inch being involved ina commercial embodiment of the invention.

Furthermore, as it is the inner piston part 176 with the lessereffective area acted on by diaphragm 172 that presses the diaphragm 170against seat 120, and the pressure differentials acting on the valvemember 114 is closely controlled by accurate proportioning of theexposed areas of the diaphragms, damaging type crushing of the diaphragm170 against the valve seat 120 is avoided.

The O-ring 250 is a commercially available product made fromflurosilicone, and in use is approximately as flexible at a minus 60degrees F. as a standard AB grade buna O-ring is at room temperatures.

It will be noted that the valve device 64 involves no sliding seals(such as piston rings, cups or seal rings) and thus this valve devicedoes not require lubrication either initially or during its operation.

The volume reservoir 66 receives its air charge from brake cylinder pipe24 directly through passage 90 and thus is upstream of the air flow fromthe brake cylinder as well as the outer chamber 118 of the differentialvalve device 64. The volume reservoir 66 will thus be at the pressure ofthe chamber 116. Its purpose is to insure harmonious operation of thecar equipped with the assembly 61 with other cars in the train that havestandard AAR brake equipment. The size of the reservoir is to beproportioned so that full service and emergency equalization pressuresmeet AAR standards. Volume reservoir 66 thus accepts the air from thebrake cylinder pipe that is not needed by the brake cylinder, due to thereduced pressures of operation involved (beyond minimum serviceapplications), and makes this air available as the pressure fluidback-up that insures full control valve compliance with AAR standards.

The foregoing description and the drawings are given merely to explainand illustrate the invention and the invention is not to be limitedthereto, except insofar as the appended claims are so limited, sincethose skilled in the art who have the disclosure before them will beable to make modifications and variations therein without departing fromthe scope of the invention.

We claim:
 1. In railroad car air brake equipment including a brakecylinder pipe connected to the brake cylinder head for communicatingfluid under pressure to the brake cylinder from the outlet of the brakecylinder pipe to the inlet of the brake cylinder head, a modulatingvalve assembly therefor for supplying the braking pressure fluid to thebrake cylinder at a pressure that is a predetermined percentage of thepressure fluid in the brake cylinder pipe for brake service strokesabove minimum service applications, said assembly comprising:a bracketplate connected in the brake cylinder pipe to define the brake cylinderpipe into upstream and downstream sections on either side of same withregard to the direction of fluid flow through the brake cylinder pipe onbrake service strokes of the equipment, said bracket plate being formedto define a first passage communicating with the brake cylinder pipeupstream section and a second passage communicating with the brakecylinder pipe downstream section, a modulating valve device carried bysaid bracket plate, said valve device comprising: a housing defining acavity, a differential valve member mounted across said cavity to definefirst and second chambers on either side of said valve member and forflexing movement laterally of said valve member, said bracket platefirst passage being in free communication with said first chamber, anannular valve seat positioned in said first chamber adjacent said valvemember, with said bracket plate second passage being in communicationwith said first chamber through said valve seat, and said valve memberbeing mounted to be flexed against said seat for sealing offcommunication, said second chamber being in free communication with saidbracket plate second passage, said valve member having exposed in saidchambers on either side of same working areas of which the working areaexposed to said second chamber is greater than the working area of samethat is exposed to said first chamber by a predetermined ratio, wherebywhen said chambers are subject to fluid pressure in said passages, saidvalve member will be subject to a differential pressure force biasingsame toward said seat, means for spring biasing said valve member awayfrom said seat that is overcome when said differential force reaches apredetermined amount, and check valve means in shunting relation to saidseat for releasing fluid under pressure in said brake cylinder andsecond passage to said first passage when said brake cylinder pipe isfree of the fluid under pressure.
 2. The valve assembly set forth inclaim 1 wherein:said bracket plate is connected into the brake cylinderpipe between a pair of flange type fittings through which the respectivebrake cylinder pipe sections respectively communicate, and means forfixing said fittings against said bracket plate, said bracket plateincluding a bracing foot for fixing said bracket plate to a support thatis stationary relative to same to brace said bracket plate.
 3. The valveassembly set forth in claim 1 including:a volume reservoir carried bysaid bracket plate, same volume reservoir being in communication onlywith said first passage for accepting from said brake cylinder pipeupstream section on brake service strokes of the equipment the pressurefluid not needed by the brake cylinder for brake service strokes aboveminimum service applications.
 4. For use with railroad car air brakeequipment including a brake cylinder pipe connected to the brakecylinder head for communicating fluid under pressure to the brakecylinder from the brake cylinder pipe to the inlet of the brake cylinderhead,a modulating valve for supplying the braking pressure fluid to thebrake cylinder from the brake cylinder pipe at a pressure that is apredetermined percentage of the pressure fluid in the brake cylinderpipe for brake service strokes above minimum service applications, saidmodulating valve comprising: a housing defining a cavity, a differentialvalve member mounted across said cavity to define first and secondchambers on either side of said valve member and for flexing movementlaterally of said valve member, first means for connecting the brakecylinder pipe in free communication with said first chamber, an annularvalve seat positioned in said first chamber adjacent said valve member,second means for connecting the brake cylinder inlet in communicationwith said first chamber through said valve seat, said valve member beingmounted to be flexed against said seat for sealing off communication ofsaid second connecting means to said first chamber, said second chamberbeing in free communication with said second connecting means, saidvalve member having exposed in said chambers on either side of sameworking areas of which the working area exposed to said second chamberis greater than the working area of same that is exposed to said firstchamber by a predetermined ratio, whereby when said chambers are subjectto fluid pressure in said passages, said valve member will be subject toa differential pressure force biasing same toward said seat, and meansfor controlling the movement of said valve member toward and againstsaid valve seat for supplying the braking pressure fluid to said brakecylinder through said valve at one hundred percent brake cylinder pipepressure level for minimum service brake applications and at apredetermined percent of brake cylinder pipe pressure levels for brakingstrokes beyond minimum service applications, said controlling meanscomprising: means for spring biasing said valve member away from saidseat, and lost motion means within said valve member and subject to saiddifferential pressure force and said spring biasing means operative toregulate the seating of said valve member against said seat to providesaid pressure levels of said braking fluid to said braking cylinder, andcheck valve means in shunting relation to said seat for releasing fluidunder pressure in the brake cylinder and said second connecting means tosaid first connecting means when the brakes are released.
 5. Themodulating valve set forth in claim 4 wherein said differential valvemember comprises:a pair of spaced apart diaphragms spanning said cavityand having their rims mounted in sealed relation within said housing todispose said diaphragms, to define said valve member working areas, anda composite piston interposed between said diaphragms including an innerpart centered with respect to and overlying said seat, and an outer partin circumambient relation to said inner part, said piston parts at theirrespective opposed ends being in close fitting relation to saiddiaphragms and defining working surfaces for engagement with same formovement of said piston parts thereby laterally of said valve member,said piston outer part having a bore receiving said piston inner part,with said piston outer part bore being larger than said seat whereby ofsaid piston parts, on movement of same in the direction of said seat,said piston inner part seats said valve member against said seat, saidspring biasing means acting on said valve member about said seat andcoaxially of said piston parts.
 6. The modulating valve set forth inclaim 5 wherein:said spring biasing means acts against one of saidpiston parts, with the working surfaces of the other piston part havingan area ratio that is the same as said predetermined ratio and with thelarger of same directed toward said second chamber, and with the workingsurfaces of said one of said piston parts having an area ratio that isless than said predetermined ratio and with the larger of said directedtoward said second chamber.
 7. The modulating valve set forth in claim 6wherein:said predetermined ratio is in the range of from about fifty toabout sixty percent, and said less ratio is on the order of thirty-fivepercent.
 8. The modulating valve set forth in claim 6 wherein:said onepiston part is the outer piston part.
 9. The combination set forth inclaim 6 wherein:said piston parts are movable relative to each otherlaterally of said diaphragms, said housing defining a stop limitingmovement of said piston outer part in the direction of said seat shortof that which by itself would bring said valve member into seatingrelation with said seat, said piston inner part being mounted withinsaid piston outer part for lost motion movement laterally of said valvemember such that when said piston outer part is seated against saidhousing stop, said piston inner part under the action of saiddifferential force may seat said valve member against said seat.
 10. Thecombination set forth in claim 9 wherein:said spring biasing meanscomprises a compression spring received about said seat in circumambientrelation thereto, with said seat being interposed between said housingand the valve member diaphragm facing said seat, said differential forceseating said diaphragm against said seat for sealing off said secondconnecting means from said first chamber.
 11. In railroad car air brakeequipment including a brake cylinder designed for use with cast ironshoes, and a brake cylinder pipe connected to the brake cylinder forcommunicating fluid under pressure from the brake cylinder pipe to thebrake cylinder, the method of supplying the braking pressure fluid tothe brake cylinder from the brake cylinder pipe at a pressure thatconverts the brake cylinder for use with composition shoes,said methodcomprising: feeding the pressure fluid at one hundred percent of thebrake cylinder pipe pressure for minimum service brake applications tothe brake cylinder up to at least ten psi for overcoming rigging staticpreloads for effecting brake shoe braking contact with the car wheelswith predetermined minimum force, and for full service and emergencybrake applications feeding the pressure fluid at one hundred percent ofthe brake cylinder pipe pressure to the brake cylinder up to at leastten psi for overcoming said rigging static preloads for effecting saidbrake shoe braking contact with said predetermined minimum force, andwhen the brake cylinder pipe pressure reaches a predetermined levelabove about ten psi, feeding the pressure fluid to the brake cylinder ata lower predetermined pressure level to provide a composition shoebraking force that is a predetermined percentage of the braking forcerequired for cast iron shoes.
 12. The method set forth in claim 10wherein:said predetermined brake cylinder pipe pressure level lies inthe range of from about twelve psi to about eighteen psi.
 13. The methodset forth in claim 11 wherein:said predetermined percentage of brakingforce lies in the range of from about fifty percent to about sixtypercent.
 14. The method set forth in claim 10 wherein:for said fullservice and emergency brake applications, the pressure fluidrepresenting the excess of that above said predetermined lower level inthe brake cylinder pipe is stored and made available for fluid pressureback up purposes.